Printing directly from CSG is much more robust than using the flakey
(literally) STL file format. A CSG file can be wrong – we can all make
mistakes – but, unlike STL, it always represents an unambiguous solid.
It should also be faster (5%)……..
Finally, it should allow us easily to do fancy things like filling
solids with scalar and vector fields representing build parameters, so
you can have an object that is flexible (and/or green) at one end and
rigid (and/or blue) at the other.

Visit the RepRap Wiki for instructions on how to use this process on your RepRap.

Perhaps this will actually pave the way to better communicate multiple materials to Objet 3D printers which currently require multiple STL files to create multiple material parts?

There are loads of good things about AMFF, but my understanding is the 3D printers have to translate curved triangles from the file into points, with triangles, so all of the grunt work is transferred from the 3D modelling software to the 3D printer.

We do need a better way to deal with more complex materials, let’s see who gets there first/best ?